The 1841 census in Patrick shows:-

Thomas Shimmin 25
Ann 25
Eleanor 3

This age would rule out the son of Philip Shimmin and Cath. Quine.

IGI has other children for Thomas and Ann, in particular Ann 1842.
The ' Find a Grave' site shows a Shimmin headstone at JoDaviess Cemetery which includes a Thomas Shimmin 31? in 1849 and an Ann 11 in 1853. There is also a Jane.

Len Faragher